**Topic**

A salesperson will receive a basic salary of 5 million VND per month and a commission of 5% if the total revenue is over 10 million VND for the month. In addition, if the monthly sales volume is 20 million VND or more, the salesperson receives an additional bonus of 500 thousand VND.

a) Express the employee’s monthly income as a function of sales

b) If the employee’s monthly sales is VND 30 million, how much salary will that employee receive?

**Solution method – See details**

Let \(x\) be the sales and \(y\) the corresponding income of the employee, based on the data of the problem, make a function representing \(y\) through \(x\) across intervals

**Detailed explanation**

a) Let \(x\) (million dong) be the sales revenue and \(y\) (million dong) is the respective monthly income of that party. We have a function that represents the employee’s monthly income by sales as follows (unit: million dong):

\(y = \left\{ \begin{array}{l}5;0 \le x \le 10\\5 + 0.05x;10 < x < 20\\5,5 + 0.05x;x \ ge 20\end{array} \right.\)

b) If \(x = 30 > 20\) then \(y = 5.5 + 0.05 \times 30 = 7\) (million VND)

So that employee will receive 7 million dong.